Simple preparation method of high-purity formamidine hydriodate with controllable crystal form

Abstract

The invention belongs to the technical field of perovskite solar cell material preparation, and particularly provides a simple preparation method of high-purity formamidine hydriodate with controllable crystal form, which comprises the steps of feeding, concentrating, washing, dissolving, crystallizing, washing, drying and the like. The method can be used for synthesis in a room-temperature laboratory, has few steps, is simple to operate, and obviously reduces the difficulty in process production. The crystal is separated out by cooling instead of a poor solvent for recrystallization, and the crystal form of the product can be controlled simply by a simple programmed cooling program with high operability. And meanwhile, by adding the washing procedure, the recrystallization frequency is reduced, the use of an organic solvent is greatly reduced, the post-treatment complexity of the product is also reduced, and the phenomenon that the product is heated and exposed to light in the post-treatment process to generate impurities is effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of perovskite solar cell materials, and specifically provides a preparation method of high-purity formamidinium hydroiodide that is simple and can control the crystal form. Background Art

[0002] In recent years, perovskite solar cells have become one of the research hotspots in the new energy field due to their excellent performance and broad application prospects. Perovskite materials are usually described by the chemical general formula ABX3, where A is an organic or inorganic cation, B is a metal cation (such as , ), and X is a halogen anion (such as , , ). Among them, formamidinium hydroiodide is often used as the source of A-site cations and reacts with PbI2 or other metal halides to construct organic-inorganic hybrid perovskites (such as ). Formamidinium hydroiodide (FAI) is a chemical that is a white crystal at room temperature, with the molecular formula CH5N2I, and is an important organic compound.

[0003] At present, there are problems such as complex processes, low yields, low purity, and poor stability in the preparation methods of formamidinium hydroiodide. Therefore, it is of great significance to develop a preparation method of formamidinium hydroiodide with a simple process, environmental friendliness, high yield, and high purity. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a preparation method of high-purity formamidinium hydroiodide that is simple and can control the crystal form, with simple operation, mild reaction conditions, high yield, fixed crystal form of the product, and excellent quality.

[0005] The present invention is realized as follows: A preparation method of high-purity formamidinium hydroiodide that is simple and can control the crystal form is provided, including the following steps: Step 1: Feeding; Dissolve formamidinium acetate in hydroiodic acid, stir at room temperature until completely dissolved, and continue stirring and reacting for a period of time; Step 2: Concentration; Rotate and evaporate under water bath heating until a yellow solid is obtained; Step 3: Washing; Rinse several times with a poor organic solvent until the yellow solid turns white; Step 4: Dissolution; Add a good solvent to the white solid in small portions and multiple times under heating until the white solid is just completely dissolved to obtain a clear and transparent liquid, reaching a saturated state at this time; Step 5: Crystallization; The clarified transparent liquid is placed at room temperature and slowly cooled, and some white formamidine hydroiodide crystals precipitate. At this time, the crystals are needle-shaped but not completely precipitated. Subsequently, the clarified transparent liquid is transferred to a low-temperature environment and cooled for a period of time again. At this time, the formamidine hydroiodide crystals are needle-shaped and precipitated to the maximum extent. Step 6: Washing; Filter, and wash the crystals with a poor organic solvent to wash away the mother liquor. Step 7: Drying; Dry the washed crystals to obtain needle-shaped high-purity formamidine hydroiodide.

[0006] Preferably, in step 1, the mass of formamidine acetate is 7 - 80 g, the concentration of hydroiodic acid is 57%, and the volume is 8 - 90 mL. The stirring speed is 400 - 800 r / min, and the stirring reaction is continued for 10 min - 1 h.

[0007] Preferably, in step 2, water bath heating is carried out to 50 - 70 °C.

[0008] Preferably, in steps 3 and 6, the poor organic solvent is anhydrous ether or ethyl acetate, and the filtrate after rinsing is recovered and the subsequent operations of step 2 and the following steps are carried out again.

[0009] Preferably, in step 4, heating is carried out to 50–80 °C; the good solvent is anhydrous ethanol or anhydrous methanol.

[0010] Preferably, in step 5, the clarified transparent liquid is cooled and crystallized at room temperature for 1 - 12 hours, and then transferred to a low-temperature environment of -20 - 0 °C and cooled and crystallized again for 1 - 12 hours.

[0011] Preferably, in step 7, the washed crystals are placed in a vacuum drying oven and dried at 50 - 70 °C for 12 - 24 hours.

[0012] A high-purity formamidine hydroiodide is provided, which is prepared by using the above-mentioned simple and crystal form-controllable preparation method of high-purity formamidine hydroiodide.

[0013] A high-purity formamidine hydroiodide is provided for use as a source of cations in perovskite solar cell materials.

[0014] Compared with the prior art, the advantages of the present invention are as follows: The present invention can be synthesized in a normal-temperature laboratory, with few steps and simple operations, and the difficulty in industrial production is significantly reduced. Using cooling to precipitate crystals instead of using a poor solvent for recrystallization, the simple and operable programmed cooling procedure enables the simple realization of controlling the crystal form of the product. At the same time, by adding a washing process, the number of recrystallizations is reduced, the use of organic solvents is greatly reduced, and the complexity of post-treatment of the product is also reduced, effectively avoiding the generation of new impurities due to the product being heated and exposed to light during post-treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Morphology of the FAI crystal prepared in Example 1 of the present invention; Figure 2 Morphology of the FAI crystal prepared in Example 2 of the present invention; Figure 3 Morphology of the FAI crystal prepared in Example 3 of the present invention; Figure 4 Morphology of the FAI crystal prepared in Example 4 of the present invention; Figure 5 Morphology of the FAI crystal prepared in the comparative example; Figure 6 Partial 1H NMR spectrum of the FAI crystal prepared in Example 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] To make the technical solutions of the present invention and their advantages clearer, the technical solutions of the present application will be further described clearly and completely below with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only partial embodiments of the present application, which are only used to explain the present application and not to limit the present application.

[0017] Example 1

[0018] 7.04 g of formamidinium acetate and 8.5 mL of hydroiodic acid with a concentration of 57% were added to the reaction apparatus in proportion, and the mixture was stirred at a speed of 400 r / min at room temperature for 10 min to obtain a reaction solution; the solution was transferred to a rotary evaporator, the water bath temperature was set at 65°C, and the condensation temperature was set at 5°C; rotary evaporation was carried out until the solution was completely evaporated and a yellow solid appeared; the yellow solid was washed with 20 mL of anhydrous ether until it turned white to obtain a crude product. The crude product was dissolved in anhydrous ethanol to a saturated and transparent state at 65°C. First, it was transferred to a room temperature environment and left to crystallize for 3 h, and then it was transferred to a 0°C environment and left to cool and crystallize for 12 h to obtain a purified product; the recrystallized and purified product was washed several times with 20 mL of anhydrous ether again and then dried in a vacuum drying oven at 50°C for 10 h to obtain the product. After the filtrate was recovered and treated, the final yield was 85%. The morphology of the obtained FAI crystal is shown in Figure 1 .

[0019] Example 2

[0020] Add 28 g of formamidine acetate and 32 mL of 57% hydroiodic acid to the reaction apparatus in proportion, stir the reaction at a speed of 600 r / min at room temperature for 30 min to obtain a reaction solution; transfer the solution to a rotary evaporator, set the water bath temperature to 65 °C, and the condensation temperature to 5 °C; perform rotary evaporation until the solution is completely evaporated and yellow solid appears; wash the yellow solid with 40 mL of ethyl acetate until it becomes white to obtain the crude product. Dissolve the crude product in anhydrous ethanol to a saturated and transparent state under heating at 70 °C. First, transfer it to a room temperature environment and let it crystallize for 5 h, then transfer it to a 0 °C environment and let it continue to cool and crystallize for 12 h to obtain the purified product; wash the product purified by recrystallization with 40 mL of ethyl acetate multiple times and then dry it in a vacuum drying oven at 55 °C for 10 h to obtain the product. After the filtrate is recovered and processed, the final yield is 89%. The morphology of the obtained FAI crystals is shown in Figure 2 。

[0021] Example 3

[0022] Add 40 g of formamidine acetate and 44 mL of 57% hydroiodic acid to the reaction apparatus in proportion, stir the reaction at a speed of 800 r / min at room temperature for 40 min to obtain a reaction solution; transfer the solution to a rotary evaporator, set the water bath temperature to 65 °C, and the condensation temperature to 1 °C; perform rotary evaporation until the solution is completely evaporated and yellow solid appears; wash the solid with 100 mL of anhydrous ether until it becomes white to obtain the crude product. Dissolve the crude product in anhydrous methanol to a saturated and transparent state under heating at 70 °C. First, transfer it to a room temperature environment and let it crystallize for 5 h, then transfer it to a -10 °C environment and let it continue to cool and crystallize for 10 h to obtain the purified product; wash the product purified by recrystallization with 100 mL of anhydrous ether multiple times and then dry it in a vacuum drying oven at 50 °C for 12 h to obtain the product. After the filtrate is recovered and processed, the final yield is 91%. The morphology of the obtained FAI crystals is shown in Figure 3 。

[0023] Example 4

[0024] Add 80 g of formamidine acetate and 90 mL of hydroiodic acid with a concentration of 57% to the reaction apparatus in proportion, stir and react at a rotation speed of 800 r / min at room temperature for 1 h to obtain a reaction solution; transfer the solution to a rotary evaporator, set the water bath temperature to 65 °C, and the condensation temperature to 1 °C; perform rotary evaporation until the solution is completely evaporated and yellow solid appears; rinse the solid with 200 mL of ethyl acetate until it is white to obtain the crude product. Dissolve the crude product in absolute ethanol at 80 °C in a saturated and transparent state. First, transfer it to a room temperature environment and let it crystallize for 12 h, and then transfer it to a -20 °C environment and let it cool and crystallize for 12 h to obtain the purified product; wash the product purified by recrystallization with 200 mL of ethyl acetate multiple times and then dry it in a vacuum drying oven at 60 °C for 24 h to obtain the product. After the filtrate is recovered and treated, the final yield is 92%. The morphology of the obtained FAI crystal is shown in Figure 4 , and the 1H NMR spectrum is shown in Figure 6 . It can be seen from Figure 6 that except for the target peak of the product and a small amount of solvent peaks, there are no other impurity peaks. The peak area of the product is 2:2:1, corresponding to the number of hydrogen atoms in the product. The baseline of the spectrum is clean and smooth, indicating that the product is correct and has high purity.

[0025] Comparative example Add 80 g of formamidine acetate and 90 mL of hydroiodic acid with a concentration of 57% to the reaction apparatus in proportion, stir and react at a rotation speed of 800 r / min at room temperature for 1 h to obtain a reaction solution; transfer the solution to a rotary evaporator, set the water bath temperature to 65 °C, and the condensation temperature to 1 °C; perform rotary evaporation until the solution is completely evaporated and yellow solid appears; rinse the solid with 200 mL of ethyl acetate until it is white to obtain the crude product. Dissolve the crude product in absolute ethanol at 80 °C in a saturated and transparent state. Transfer it to a -20 °C environment and let it cool and crystallize for 24 h to obtain the purified product; wash the product purified by recrystallization with 200 mL of ethyl acetate multiple times and then dry it in a vacuum drying oven at 60 °C for 24 h to obtain the product. The obtained FAI crystal is shown in Figure 5 . Through the comparison of Figure 4 and Figure 5 , it can be seen that in the comparative example, due to the too large temperature difference, the supersaturation of the mother liquor increases rapidly, and nucleation occurs explosively in the system. The too fast growth rate results in the crystal presenting a fine granular shape; while in Example 4, because it is first placed at room temperature, the temperature difference is reduced, thereby reducing the supersaturation of the mother liquor and slowing down the crystal nucleation rate, resulting in fewer formed crystal nuclei. After a period of stable crystal nuclei, it is then placed in a low temperature state to further reduce the supersaturation. At this time, the temperature difference causes the crystal to grow along the dominant direction of the (001) plane to form a long strip shape. To sum up, this invention achieves the purpose of controlling the crystal shape to be needle-like through a simple and operable staged temperature reduction.

Claims

1. A preparation method of high-purity formamidine hydroiodide that is simple and can control the crystal form, characterized in that, It includes the following steps: Step 1: Feeding materials; Dissolve formamidine acetate in hydroiodic acid, stir at room temperature until completely dissolved, and continue stirring for a period of time; Step 2: Concentration; Rotate and evaporate under water bath heating until a yellow solid is obtained; Step 3: Washing; Rinse several times with a poor organic solvent until the yellow solid turns white; Step 4: Dissolution; Add a good solvent to the white solid in small portions multiple times under heating until the white solid is just completely dissolved to obtain a clear and transparent liquid, reaching a saturated state at this time; Step 5: Crystallization; Place the clear and transparent liquid at room temperature and slowly cool it to precipitate some white formamidine hydroiodide crystals. At this time, the crystals are needle-shaped but not completely precipitated; then transfer the clear and transparent liquid to a low-temperature environment and cool it for another period of time. At this time, the formamidine hydroiodide crystals are needle-shaped and precipitated to the maximum extent; Step 6: Washing; Filter, rinse the crystals with a poor organic solvent to wash away the mother liquor; Step 7: Drying; Dry the washed crystals to obtain needle-shaped high-purity formamidine hydroiodide.

2. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, characterized in that, In Step 1, the mass of formamidine acetate is 7 - 80 g, the concentration of hydroiodic acid is 57%, and the volume is 8 - 90 mL. The stirring speed is 400 - 800 r / min, and the continuous stirring reaction is 10 min - 1 h.

3. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, characterized in that, In Step 2, heat the water bath to 50 - 70 °C, and the condensation temperature is 1 - 5 °C.

4. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, characterized in that, In Steps 3 and 6, the poor organic solvent is anhydrous ether or ethyl acetate, and the filtrate after rinsing is recycled for Step 2 and subsequent operations.

5. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, wherein, In Step 4, heat to 50–80 °C; the good solvent is anhydrous ethanol or anhydrous methanol.

6. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, characterized in that, In Step 5, the clear and transparent liquid is cooled and crystallized at room temperature for 1 - 12 hours, and then transferred to a low-temperature environment of -20 - 0 °C and cooled and crystallized again for 1 - 12 hours.

7. The preparation method of the simple and polymorph-controllable high-purity formamidine hydroiodide according to claim 1, characterized in that, In Step 7, place the washed crystals in a vacuum drying oven and dry them at 50 - 70 °C for 12 - 24 hours.

8. A high-purity formamidine hydroiodide, characterized in that, It is prepared by using the preparation method of high-purity formamidine hydroiodide which is simple and can control the crystal form described in any one of claims 1 - 7.

9. Use of the high-purity formamidine hydroiodide according to claim 8, characterized in that, It is used as the source of cations in perovskite solar cell materials.

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